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Hagia Sophia, one of history's greatest buildings, is in danger

It’s a building you could argue has a greater history than any other. Hagia Sophia was the world’s largest cathedral for almost 1,000 years before being converted to a mosque, then a museum, then a church again. In that time it’s survived wars, looting, fires and multiple earthquakes — just about.

But there are fears the next big quake could be catastrophic for the structure, which is why it’s now going through an extensive restoration, including reinforcements to its iconic dome. This is the story of Istanbul’s remarkable landmark, and what’s being done to save it.